Fiber optic cables have been traditionally placed at a depth of 4 to 6 feet below the road surface in a conduit structure that involves excavation, refilling, and repairing of the road surface.
However, fiber optic cables have been recently installed within the pavement of a road in shallow grooves, or channels. These shallow grooves are typically about 2 to 6 inches deep. Fiber optic cables that are provided within a shallow groove in the pavement can be provided to individual customers at a lower cost than cables provided in deeper grooves.
U.S. Pat. No. 6,371,691 (“the '691 patent”), for example, is directed to a method for introducing a micro-cable into a shallow channel in the ground. However, the fiber optic cables of the '691 patent have not been designed specifically for use in the harsh pavement environment. Because shallow groove cables are provided within the pavement, the cables are subject to extreme temperatures caused by the pavement's exposure to the sun. Not only do these extreme temperatures cause the cable to rapidly degrade, but in addition, the high temperatures also can cause the cable to expand linearly.
This expansion can cause the cable to press against the fill material, such as a sealant, provided in the groove above the cables. If the linearly expanding cable pushes against the fill material with a strong enough force, the cable can cause the fill material to push above the road's surface.